G. Cardoso

Development of high data readout rate pixel module and detector hybridization at Fermilab

This paper describes the baseline design and a variation of the pixel module to handle the data rate required for the BTeV experiment at Fermilab. The present prototype has shown good electrical performance characteristics. Indium bump bonding is proven to be capable of successful fabrication at 50 micron pitch on real detectors. For solder bumps at 50 micron pitch, much better results have been obtained with the fluxless PADS processed detectors. The results are adequate for our needs and our tests have validated it as a viable technology.

Development of a high density pixel multichip module at Fermilab

At Fermilab, both pixel detector multichip module and sensor hybridization are being developed for the BTeV experiment. The module is composed of three layers. The lowest layer is formed by the readout integrated circuits (ICs). The backs of the ICs are in thermal contact with the supporting structure, while the tops are flip-chip bump bonded to a pixel sensor. A low mass flex-circuit interconnect is glued on the top of this assembly, and the readout IC pads are wire-bonded to the circuit. The BTeV pixel detector is based on a design relying on this hybrid approach. This method offers maximum flexibility in the development process, choice of fabrication technologies, and the choice of sensor material. This paper presents strategies to handle the required data rate and performance characteristics of the pixel module prototypes.

Study of indium and solder bumps for the BTeV pixel detector

The pixel detector proposed for the BTeV experiment at the Fermilab Tevatron will use bump-bonding technology based on either Indium or Pb/Sn solder to connect the front-end readout chips to the silicon pixel sensors. We have studied the strength of the bumps by visual inspection of the bumps bonding silicon sensor modules to dummy chips made out of glass. The studies were done before and after thermal cycles, exposed to intense irradiation, and with the assemblies glued to a graphite substrate. We have also carried out studies on effects of temperature changes on both types of bump bonds by observing the responses of single-chip pixel detectors to an Sr/sup 90/ source. We report the results from these studies and our plan to measure the effect of cryogenic temperatures on the bumps.

Performance of prototype BTeV silicon pixel detectors in a high-energy pion beam

Abstract The silicon pixel vertex detector is a key element of the BTeV spectrometer. Sensors bump bonded to prototype front-end devices were tested in a high-energy pion beam at Fermilab. The spatial resolution and occupancies as a function of the pion incident angle were measured for various sensor-readout combinations. The data are compared with predictions from our Monte Carlo simulation and very good agreement is found.

CDF run IIb silicon detector: the innermost layer

The innermost layer (L00) of the Run IIa silicon detector of CDF was planned to be replaced for the high luminosity Tevatron upgrade of Run IIb. This new silicon layer (L0) is designed to be a radiation tolerant replacement for the otherwise very similar L00 from Run IIa. The data are read out via long, fine-pitch, low-mass cables allowing the hybrids with the chips to sit at higher z(/spl sim/70 cm), outside of the tracking volume. The design and first results from the prototyping phase are presented. Special focus is placed on the amount and the structure of induced noise as well as signal-to-noise values.

Single event effects in the pixel readout chip for BTeV

In future experiments the readout electronics for pixel detectors is required to be resistant to a very high radiation level. In this paper we report on irradiation tests performed on several preFPIX2 prototype pixel readout chips for the BTeV experiment exposed to a 200 MeV proton beam. The prototype chips have been implemented in commercial 0.25 {micro}m CMOS processes following radiation tolerant design rules. The results show that this ASIC design tolerates a large total radiation dose, and that radiation induced Single Event Effects occur at a manageable level.

Radiation tolerance of prototype BTeV pixel detector readout chips

High-energy and nuclear physics experiments need tracking devices with increasing spatial precision and readout speed in the face of ever-higher track densities and increased radiation environments. The new generation of hybrid pixel detectors (arrays of silicon diodes bump-bonded to arrays of front-end electronic cells) is the state-of-the-art technology able to meet these challenges. We report on irradiation studies performed on BTeV pixel readout chip prototypes exposed to a 200-MeV proton beam at the Indiana University Cyclotron Facility. A prototype pixel readout chip (preFPIX2) has been developed at Fermilab for collider experiments and implemented in standard 0.25-/spl mu/m CMOS technology following radiation-tolerant design rules. The chip contains a variety of functional blocks (analog front ends, registers, state machines, and digital-to-analog converters). The tests confirm the radiation tolerance to proton total dose up to 87 Mrad of all of these circuits. In addition, nondestructive radiation-induced single-event upsets have been observed in on-chip static registers, and the single-bit upset cross-section has been extensively measured.

Study of temperature dependence of bump bonding for the BTeV pixel detector

The pixel detector proposed for the BTeV experiment at the Fermilab Tevatron will use bump-bonding technology based on either Indium or Pb/Sn solder to connect the front-end readout chips to the silicon pixel sensors. We have studied the behavior of the bumps by visual inspection of the bumps bonding silicon sensor modules to dummy chips made out of glass. The studies were done before and after thermal cycles, exposure to intense irradiation, and with the assemblies glued to a graphite substrate. We have also carried out studies on effects of temperature changes on both types of bump bonds by observing the responses of single-chip pixel detectors to a /sup 90/Sr source. We report the results from these studies as well as the noise and threshold behavior of the pixel readout at various temperatures.

Temperature dependence of pixel multichip module operating performance

At Fermilab, a research program to develop a pixel detector for the BTeV experiment has been ongoing for the last several years. The basic building block of the pixel detector is the pixel multichip module. Prototypes have been built and characterization tests have been performed to verify that the pixel module will meet the stringent requirements of the experiment. One of these requirements is that the operating temperature of the detector will be at -5/spl deg/C, which imposes severe constraints on the pixel multichip module packaging design. This paper presents the temperature dependence of prototypes of the pixel multichip module.

Distributed Data Acquisition and Storage Architecture for the SuperNova Acceleration Probe

The SuperNova acceleration probe (SNAP) instrument is being designed to collect image and spectroscopic data for the study of dark energy in the universe. This paper describes a distributed architecture for the data acquisition system which interfaces to visible light and infrared imaging detectors. The architecture includes the use of NAND flash memory for the storage of exposures in a file system. Also described is an FPGA-based lossless data compression algorithm with a configurable pre-scaler based on a novel square root data compression method to improve compression performance. The required interactions of the distributed elements with an instrument control unit will be described as well.